Visual recordings of moving things are generally made up of sequences of successive of images. Each such image represents a scene at a different time or range of times. This invention relates to recordings consisting of sequences of images such as are found, for example, in video, film and animation.
The common video standard PAL used in Europe comprises 25 frames per second. This means that an hour of video will consist of nearly 100,000 frames. Other video formats, such as the NTSC standard used in the USA and Japan, have similar number of frames per hour as PAL.
A requirement for a human operator to locate accurately and to access reliably a particular frame from within many can arise. One application where this requirement arises is video editing. In this case, the need may not just be for accurate access on the scale of individual frames, but also easy access to different scenes many frames apart. In other words, there is a need to be able to access video frames over a range of time scales which may be up to five or six orders of magnitude apart.